The present invention relates to a bandage that may be applied directly to the patient's skin and more particularly to a silicone impregnated occlusive dressing for a penetrating thoracic wound.
The process of breathing depends on maintaining a proper pressure differential between the pleural cavity and the outside environment. Normally, visceral and parietal pleura are separated by the pleural space which is filled with pleural fluid. When one's diaphragm and intercostal muscles contract during inspiration, the rib cage expands, pulling the pleural pleura away from the visceral pleura. A negative pressure in the pleural space ensures that the visceral pleura follows the pleural pleura as it expands outwardly. A net negative pressure is then developed within the lungs themselves, and positive atmospheric pressure forces air into the lungs. This is the phenomenon know as inspiration.
In penetrating thoracic trauma, an object like a bullet, knife or metal fragment penetrates the chest wall or both the chest wail and the lung itself and exposes the pleural space to the atmospheric pressure of the outside environment. When the normal negative pressure of the pleural space is exposed to the more positive atmospheric pressure, outside air flows into the pleural space through the wound or through the punctured lung causing an open pneumothorax to develop. The net negative pressure within the plural space diminishes. The visceral and parietal pleura separate as the outside air compresses the lung and forces the lung and chest wall farther apart. As air and other fluids like blood released by vessels damaged in the trauma continue to enter the pleural space, ventilation of the affected, and now compressed, lung becomes increasingly difficult. The pressure needed to inflate the lung via normal physiological mechanisms is no longer attainable. As even more fluid continues to enter the pleural space through the open wound, the heart, the great vessels of the heart and the opposite lung become compressed under the increasingly positive pressure in the thorax. The opposite lung eventually collapses, and blood flow to and from the heart decreases. Cardiac output falls significantly, cardio-pulmonary collapse and unconsciousness occur, followed soon thereafter by cardio-pulmonary arrest and death.
It is, therefore, important that the wound dressing applied in the field seals the chest wall to prevent air from entering the pleural space through the wound. At the same time the dressing must allow air entering the pleural space through a punctured lung and blood that may have leaked into the pleural space as a result of the trauma, be allowed to evacuate from the wound. Such a dressing allows the patient to at least partially reestablish the proper pressure differential in the pleural cavity. With the proper dressing applied quickly in the field, the patient's natural reflex to continue to attempt to breathe can be accommodated and even facilitated. A dressing designed to treat a penetrating thoracic chest wound must be able to seal the wound at sometimes and, equally importantly, allow it to open at others.
There is particularly a need for an improved field dressing for penetrating thoracic wounds to be used by emergency medical personnel at the scene of an injury. Penetrating thoracic trauma is unique because wounds which compromise the chest wall are often rapidly fatal. As explained above, if a bullet, knife or other high force projectile, like metal fragments from a motor vehicle accident, punctures the chest wall, then the normal mechanism by which the lungs operate is affected, with life threatening consequences.
The current occlusive dressings used to treat penetrating thoracic trauma in the field is a gauze pad impregnated with petroleum jelly. The occlusive gauze prevents further entry of air into the pleural space, and thereby prevents further damage resulting from positive intrapleural pressure. In the event that the lung itself has been punctured in the injury, an increase in intrapleural pressure may occur in spite of, and perhaps even because of, a properly applied occlusive dressing with an adequate seal. The resulting tension pneumothorax is often rapidly fatal. To correct for this possibility, it is advisable that the occlusive gauze dressing be taped to the skin on only three sides of the usually square gauze pad, thereby allowing air from a pleural space to escape via the untaped fourth side of the dressing. The often stressful environment surrounding patients afflicted with penetrating thoracic trauma and the "load-and-go" speed with which emergency service personnel must work, can make it difficult to properly apply such a wound dressing. The result can be either an inadequate seal which allows further development of an open pneumothorax, or a totally occlusive dressing, which does not allow for the passive relief of a tension pneumothorax.
The use of petroleum as the occlusive medium for the dressing can also be a problem. One of the first treatment modalities for penetrating thoracic trauma is the administration of oxygen. The application of petroleum products to a wound from which 100% oxygen may be flowing, in the oxygen rich environment found in the patient compartment of an ambulance, introduces the risk of fire. Petroleum products can also cause death to lung tissue upon contact. In the event that a petroleum product does contact the lung through the open chest wound, the possibility of tissue necrosis is significant.
Also, petroleum occlusive dressings that are adapted for this purpose in the field are removed from sterile packaging and applied to the open wound with non-sterile hands. The risk of infection can be high. Also, the size of the petroleum occlusive dressings used currently is adequate to cover small or single entrance wounds like bullet wounds and puncture type stab wounds. It is, however, too small to adequately treat larger wounds like deep slashing stab wounds, shotgun blasts and injuries due to metal motor vehicle fragments.
There is a need for a compact specially designed wound dressing for penetrating thoracic trauma which is sterilely packaged and can be quickly and easily applied to the wound in the field with a minimum risk of contaminating the dressing. The dressing should also be large enough to cover the variety of types of wounds that are found in the field. It is also important to eliminate the petroleum jelly and to use an occlusive medium which is more compatible with the other therapies that need to be applied to a patient suffering from a penetrating thoracic trauma.